PHOTO: CREDIT HERE
Planet Earth
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PHOTO: ALEXANDER SEMENOV
Many invertebrates, such as salamanders and sea stars, can regrow a body part
if they lose one. That’s what biologist Michael Abrams expected to happen when
he removed two of eight arms from a young moon jelly (Aurelia aurita). But when
Abrams checked on the experiment, “he started yelling... ‘You won’t believe
this—you’ve got to come here and see!’ ” recalls Abrams’s doctoral adviser, Lea
Goentoro of Caltech in Pasadena. Instead of regrowing limbs, the jellyfish had
rearranged its remaining arms so they were spaced equidistantly around its body.
For a young moon jelly, or an adult (below), being symmetrical is crucial for
movement and feeding. For Abrams’s test animal to achieve that, muscles
contracted in its body, which pushed and pulled the remaining arms until they
were once again evenly spaced. The scientists had stumbled upon a phenome-
non completely new to science, which they call “symmetrization.” It’s clearly an
important way in which jellyfish heal themselves—and, says Goentoro, it could
prove useful to scientists studying regenerative mechanisms.
— Carrie Arnold
How a
Jellyfish
Re-arms
LEARN MORE ABOUT OCEANS In his new book, Pristine Seas: Journeys to the Ocean’s Last Wild Places, National
Geographic Explorer-in-Residence Enric Sala takes readers to ten of the last wild places in Earth’s oceans. The book goes
on sale September 22 wherever books are sold and at shopng.com/books. On television, the latest Pristine Seas adventure,
Behind Russia’s Frozen Curtain, premieres on the Nat Geo WILD channel on Sunday, September 20 at 9 p.m. ET.
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